IllegalArgumentExcetion while transform OpenFlow model normalizednode to Json

I want to transform OpenFlow Models (Flow, Group, Meter, e.g) to JsonObjects String. I have made NormalizedNode from Flow successfully, but when I use JSONNormalizedNodeStreamWriter as a streamWriter (to write JsonString from Normalized), I got IllegalArgumentExcetion. I want to know if the OF Models are supported to translate to JsonObject already, and would you give correct suggestions to operate?

Following is the exception logs:

java.lang.IllegalArgumentException: List item is not appropriate
at com.google.common.base.Preconditions.checkArgument(Preconditions.java:122)[41:com.google.guava:18.0.0]
at org.opendaylight.yangtools.yang.data.impl.codec.SchemaTracker.startListItem(SchemaTracker.java:144)[57:org.opendaylight.yangtools.yang-data-impl:1.0.4.Boron-SR4]
at org.opendaylight.yangtools.yang.data.codec.gson.JSONNormalizedNodeStreamWriter.startMapEntryNode(JSONNormalizedNodeStreamWriter.java:174)[60:org.opendaylight.yangtools.yang-data-codec-gson:1.0.4.Boron-SR4]
at org.opendaylight.yangtools.yang.data.api.schema.stream.NormalizedNodeWriter$OrderedNormalizedNodeWriter.writeMapEntryNode(NormalizedNodeWriter.java:267)[56:org.opendaylight.yangtools.yang-data-api:1.0.4.Boron-SR4]
at org.opendaylight.yangtools.yang.data.api.schema.stream.NormalizedNodeWriter.wasProcessedAsCompositeNode(NormalizedNodeWriter.java:208)[56:org.opendaylight.yangtools.yang-data-api:1.0.4.Boron-SR4]
at org.opendaylight.yangtools.yang.data.api.schema.stream.NormalizedNodeWriter.write(NormalizedNodeWriter.java:100)[56:org.opendaylight.yangtools.yang-data-api:1.0.4.Boron-SR4]
....